3W: 2 fixed middle autosize

I am trying to build a ui with three cells using the 3W layout. I want the middle cell to be auto-size and the two (left and right) cells to be fixed 200px. This is the code that I am trying to use:

Any help would be appreciated! I am on 5.02 Enterprise version.

Please, try to add the following code:
It will enable the autosizing for the cell “b” in your layout.